Application of pressurized circulating fluidized bed technology for combined cycle power generation

Ahlstrom Pyropower, Inc. (API) pioneered the development of atmospheric circulating fluidized bed (ACFB) technology. The sustained success with ACFB and continued research in ACFB systems has led Ahlstrom towards the development of pressurized circulating fluidized bed (PCFB) technology. Since the mid-1980s many components of the PCFB combined cycle power plant were developed. Based on the component development experience, a 10 MW_th PCFB pilot plant was built to support the design of commercial size PCFB units.The PCFB pilot plant has operated over 4500 hours since its commissioning in mid 1989. Five types of coals and five types of sorbents have been tested. Emissions and load following performance of the pilot plant have demonstrated that the PCFB performs significantly better than required under the current stringent environmental standards. The sulfur capture has been 95 to 98%; the NO_x level with SNCR is less than 25 mg/MJ; the ash generated from the PCFB is less basic than the ash from conventional system.API, under the U.S. Department of Energy's Clean Coal Technology III program, was awarded a contract to build a nominal 80 MW_e PCFB combined cycle repowering unit. The unit is scheduled for commissioning in early 1997. API has also performed design studies for larger capacity units in the range of 100 – 400 MW_e. These designs include a second generation PCFB technology combined cycle system for the use of high ash coals. The second generation PCFB technology involves partial gasification of coal and the use of the syngas to heat up the PCFB exhaust flue gas to 1300°C at the gas turbine inlet. This paper, in addition to presenting the pilot plant results, summarizes the salient features of PCFB combined cycle plants for various fuels including high ash Indian coals.